Heretofore, difficulties have been encountered in precise aiming and locking of artillery weapons. Once an artillery weapon is aimed toward a target, it must be locked in position to prevent recoil forces from damaging the aiming mechanisms or altering the trajectory of a second projectile. Imperfect equilibration can also effect the trajectory; i.e., the weight of the gun tube and other tipping parts could change the point of aim if not locked in position. An early type of elevation locking mechanism consisted of simply a pin which passed through spaced holes in adjacent parts of the cannon cradle. This method allowed the weapon to be aimed only at elevations where the spaced holes aligned and the pin could be inserted. If more precise positioning was required, the entire weapon had to be tilted.
More recently artillery elevating systems utilize ball screw mechanisms which are actuated by handwheels near the weapon operator. A ball screw is a threaded shaft with a mating nut. The nut is carried by ball bearings rather than mating directly to the shaft. This greatly reduces friction, resulting in very smooth and efficient operation. The weapon must still be locked on target for reasons previously stated. Hydraulic locks have been experimented with but this required both hands and a two step operation to lock or unlock the elevating mechanism. This increases the time it takes to aim the weapon and further complicates weapon operation. Commercially available automatic clutches have also been tried but are prone to slipping when used with larger caliber weapons. While these locking systems are capable of locking at virtually any angle of elevation, they do not meet modern requirements because of these disadvantages.